Diversity, ecology and intestinal function of bifidobacteria

Abstract

The human gastrointestinal tract represents an environment which is a densely populated home for a microbiota that has evolved to positively contribute to host health. At birth the essentially sterile gastrointestinal tract (GIT) is rapidly colonized by microorganisms that originate from the mother and the surrounding environment. Within a short timeframe a microbiota establishes within the (breastfed) infant's GIT where bifidobacteria are among the dominant members, although their numerical dominance disappears following weaning. The numerous health benefits associated with bifidobacteria, and the consequent commercial relevance resulting from their incorporation into functional foods, has led to intensified research aimed at the molecular understanding of claimed probiotic attributes of this genus. In this review we provide the current status on the diversity and ecology of bifidobacteria. In addition, we will discuss the molecular mechanisms that allow this intriguing group of bacteria to colonize and persist in the GIT, so as to facilitate interaction with its host.

Figure 1

Rooted neighbour-joining tree based on the alignment (1265 nucleotides) of the 16S rRNA gene (96% of homology) sequence from the 48 so far recognized bifidobacterial taxa (Dec., 2013). The phylogenetic groups, as highlighted in grey shaded quadrangles, are the result of a previously performed multilocus analysis [9], integrated with the information resulting from the alignment of the 16S sequence of new bifidobacterial species.

Figure 2

Genome atlas of B. breve UCC2003. Surrounding the genome are schematic representations of selected genes or gene clusters that have been characterised through comparative and functional genomic approaches using B. breve UCC2003 as a model Bifidobacterium strain. The proven function of each gene/gene cluster is indicated together with the gene name and gene ID, see text for further explanations and relevant references.